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The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuousmap of forest tree density at a global scale. This mapreveals that the global numberof trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.
Forest ecosystems harbour a large proportion of global biodiversity, contribute extensively to biogeochemical cycles, and provide countless ecosystem services, including water quality control, timber stocks and carbon sequestration1-4. Our current understanding of the global forest extent has been generated using remote sensing approaches that provide spatially explicit values relating to forest area and canopy cover3,5,6. Used in a wide variety of global models, these maps have enhanced our understanding of the Earth system3,5,6, but they do not currently address population numbers, densities or timber stocks. These variables are valuable for the modelling of broad-scale biological and biogeochemical processes7-9 because tree density is a prominent component of ecosystem structure, governing elemental processing and retention rates7,9,10, as well as competitive dynamics and habitat suitability for many plant and animal species11-13.
The number of trees in a given area can also be a meaningful metric to guide forest management practices and inform decision-making in public and non-governmental sectors14,15. For example, international afforestation efforts such as the 'Billion Trees Campaign', and city-wide projects including the numerous 'Million Tree' initiatives around the world have motivated civil society and political leaders to promote environmental stewardship and sustainable land management by planting large numbers of trees14,16,17. Establishing targets and evaluating the proportional contribution of such projects requires a sound baseline understanding of current and potential tree population numbers at regional and global scales16,17.
The current estimate of global...